OBJECTIVETo analyze stress around the impacted tooth by constituting a 3-dimensional finite element model of impacted tooth, consequently offer reference basis for clinic traction treatment.

METHODSThe 3-dimensional finite element model of the impacted tooth was constituted by CT scan, append pericementum and alveolar bone model was used to constitute impacted model. 3 forces were loaded to 3-dimensional finite element model and the periodontal stress of impacted tooth was calculated.

RESULTSWhen force 1 was loaded to the model, the maximum stress was smaller, but the stress distribution was more average. When force 3 was loaded to the model, the maximum stress was larger, but the stress concentrated at the side of the force. When force 2 was loaded to the model, the stress distribution was medium.

CONCLUSIONWhen the direction of the force is in line with the central axis, the maximum stress is smaller, and the stress distribution is more average, while this has advantage to the eruption of the impacted tooth. When the direction of the force has angle with the central axis of the impacted tooth, the angle is larger, the maximum stress is larger and the stress distribution is more concentrate, and this goes against the eruption of the impacted tooth. The angle between the orientation of the traction and central axis of the impacted tooth is smaller, there are more advantages to the eruption of the impacted tooth. So the angle should be properly selected in order to make sure of the eruption of the impacted tooth. When the angle is quite large, more anchorage is needed to resist to the large force.